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2a855b644c
The list_splice_init_rcu() function allows a list visible to RCU readers to be spliced into another list visible to RCU readers. This is OK, except for the use of INIT_LIST_HEAD(), which does pointer updates without doing anything to make those updates safe for concurrent readers. Of course, most of the time INIT_LIST_HEAD() is being used in reader-free contexts, such as initialization or cleanup, so it is OK for it to update pointers in an unsafe-for-RCU-readers manner. This commit therefore creates an INIT_LIST_HEAD_RCU() that uses ACCESS_ONCE() to make the updates reader-safe. The reason that we can use ACCESS_ONCE() instead of the more typical rcu_assign_pointer() is that list_splice_init_rcu() is updating the pointers to reference something that is already visible to readers, so that there is no problem with pre-initialized values. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> |
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